Detector.



L. S. BARR.

DETECTOR.

APPLICATION FILED SEPT.10. 191s.

Patented Dec. 29, 1914.

F mun 9 26 mum 2 n ran sixa'rns PATENT DFFICE."

' LESTER STEWART BARR, OF WASHINGTON, DISTRICT or COLUMBIA; I

' IDETECTOIL To all whom it may concern:

rBe it known that-I, LESTER STEWART Bane,

I citizen of the United States, residing at Vashingtomin the District of Columbia,

, have invented a new and useful'Detector, of

which the following is a specification.

My invention relates to improvements in apparatus for Wireless or Hertzian Wave 'telegraphy, and more particularly to the class of instruments known as detectors.

In general, vit is the function of the detector to so modify or transform the currents set up in' the receiving circuit as to render them capable of acting upon the receiver proper to produce sensible signals. .Of the various types of'apparatuswvhich have beencmployed for this purpose, the type known as the crystal detector has proved the most satisfactory for general use, and it is my object toimprove the mechanical struc-,

ture of the crystal detector so as to free it from certain Well recognized mechanical faults which have hitherto operated to impair the inherent virtues of the' type.

In order that the invention 'maybe more a readily understood Iwill briefly outline. the

v contact between a metallic electrode and cerelectrical principles which underlie theac tion of this type of detector, and enumeratethe essential mechanical features of a practicalfembodiment of the apparatus.

It has been found that a small surface tain crystalline mineral substances, for instance, galena, silicon, etc, has the property of exerting a rectifying action on high frequency electrical currents. This property of the contact is somewhat elusive, almost disappearing at times withoutapparent cause and va'ryingin elficiency' at different points of thesurface and at different times. .The'pressure of contact is found to influence materially the results obtained, but this also is according to no'established principle, ar-

bit-rarily varying between moderate limits.

' the crystal and leadingin-wire;

' varying; the pressure of contact.

In general therefore the essentials of a detector of this type ares- A crystal mount-v ing providing electrical connection between An electrode mounting and electrical connection. Means for changing the. point of contact between the electrode and crystal. Means for It is my object to provide a simple and efficient device in whichthe above essentials are present and in which-especial advan- Sziecification'of Letters Batent. Patnfed D 29 1914 Application filed September 10, 1913. Serial No. 789,082. I I

- tages relating to facility of adjustment are embodied. Y Y 11th the above and otherobjects, which will appear as the description proceeds, in

- view, I have designed the" form of detector described n the. annexed specification and illustrated by the accompanying drawings,

in which a F gure 1 18 an elevation, partly in sectionof one embodiment of my invention, and

' Fig. 2 is a plan view of the same.

Like characters denote the same parts in each view. i

(1) indicates the base block of the deted tor, conveniently formed as a'rectangular plate of vulcanite. Let into the upper face of the base block so that their surfaces'shall i be flush with the same, are the metallic contact plates(2) and ('3) carrying respectively the binding posts(4:) and (5') for the leading-in and leading out conductors. The under face ofthe contact plate (2') is formed with a boss 6) which is drilled and fected by meahs of a threaded stud ('10) which is preferably formed integrally Withthe bottom of the inner steel shell- (8-) and takes into the threaded opening'in the boss ((3). The wall of the cup (7) is drilled and tapped near the bottom to receive a horizontal displacement screw (11) tlie function of which'will appear later; 7

Mounted on the contact plate is a mes I the plate. and base-block by an integral,

threaded stud (13) which passes throi'igh a countersunk bore in the base block andreformed by the countersink. The upper end" of the pillar .is enlarged at (15) a and bored horizontally to receive the needle arm (16) tallic-pillar 12), the pillar being secured to ceives a nut 14) which seats in the recess with a sliding fit; The arm (16) is secured;

inany adjustedposition by a set screw (17) in the top of the -pillan.-. The outer extremity of the needle arm is ,enlargedas at (1'8) the enlargement being drilled and tapped" vertically to receive the vertically adjustable screw (19). In the lower end of the needle screw 18 mifiinted the steel needle .(20) which forms the contact electrode of the detector. As a precaution, the head of the needle screw may be formed of a separate disk of vii lcanite or other insulating material, indibatetl at (21). In order. that the needle screw may be held against accidental rotation, the end of the arm (16) may be split asfar' back as the enlargement 18), the split end being clamped into good rictional engagement with the needle screw by means of thesniall clamping screw (22).

The apparatus above described, having been properly assembled, the cup (7) is filled about two-thirds full with an electri- (24), is placed in the cup. In general, any

crystalline mineral suitable fornse in a detector will have a specific gravity less than that or the'mercury, and the crystal will therefore float at the top of the cup. T he needle screw will then be lowered until the contact point touches the surface of the crystal. The detector being properly connected into the receiving circuit the operator will make-use of his testing buzzer in a manner'' well understood in the art, and continue to lower the needle until an approximate adjustment is obtained, as indicated by the sound heard in the ear-phones. It will be obvious that as the needle is lowered the crystal will displace more and more of the mercury and the pressure of the contact will gradually and uniformly increase. After an approximate adjustment has been obtained by lowering the needle screw, the displacement screw (11) may be brought into use to effect the final adjustment. By advancing this screw into or withdrawing it from the cup the level of the mercury there in mav be changed by infinitesimal amounts, thus ell'e cting a most delicate adjustment of the pressure of contact.

It may often happen that the particular point of the crystal on which the needle bears does not give satisfactory results, or

' that from use or other causes this particular contact has deteriorated. In either event it is only necessary to tap the crystal with messes ment of the submerged portion of the crystal. it will be apparent also that with great facility the whole surface of the crystal may be searched in order to locate the most advantageous contact, it being possible to try new'contacts as fast as thefinger can move to tap the crystal. The importance of being able to reach a new point with the least loss of time will be understood, when it is remembered that a contact may deteriorate so far as to become useless while the operator is taking a message.

It will also be noted that the effect of temperature changes upon the instrument is negligible, such changes giving only a minute difference of immersion of the crystal.

The electrical eiiiciency of this type of detector isvery high, owing to the exception ally good electrical connection furnished by the mercury; It will therefore be seen that I have provided a simple and efficient instrument in which the inherent simplicity of the crystal contact detector is conserved, and in which the necessary adjustments may be easily and quickly accomplished, and when once accomplished may he maintained.

While I have shown and described a specific embodiment of my invention, including numerous details and refinements of construction, it will be understood that this is purely illustrative and that the scope of my invention is to be determined only by the terms of the claims hereunto annexed.

What I claim is 1. In a crystal detector, a cr stal mounting comprising a receptacle, a mercury pool within the receptacle, a crystal freely floating on the surface of the mercury and spaced from the walls of the receptacle, and a contact electrode supported to bear upon the exposed upper face of the crystal, whereby the crystal may be rotated within the mercury pool to bring any point of its surface in position to contact with the electrode.

2. In a crystal detector, a crystal mount" ing comprising areceptacle, a mercury pool within the receptacle, a displacement screw for varying the level of mercury within the receptacle. a crystal freely floating on the surface of the mercury and spaced from the walls of the receptacle, and a con-tact electrode supported to bear upon the exposed upper face of the crystal, whereby the crys tal may be rotated within the mercury pool to bring any point of its surface in position to contact with the electrode.

LESTER STEWART BARR.

IE. E. KELLY. 

